1. Field of the Invention
This invention relates to a combustor which produces hot combustion gases and a stable flame that is useful in combustion processes and may especially be useful in the pyrometallurgical treatment of finely divided materials. More particularly, the invention relates to a combustor which uses a gaseous fuel such as natural gas to produce a stable flame over a wide range of combustion conditions by forming particular flow patterns in the combustor.
2. Description of the Prior Art
The basic chemistry of combustion processes has been known for many years as have simple apparatus for carrying out those processes. Nevertheless, combustion methods and apparatus vary greatly depending on the particular application involved. That variability results from the wide range of fuels, oxygen sources, flowrates, and combustor designs which may be used in a particular application to achieve specific objectives. Consequently, the parameters for a particular combustion application must be developed for that application and are not readily adapted from other different combustion applications. Exemplary of existing combustion apparatus and processes are U.S. Pat. Nos. 4,622,007, 4,797,087 and Re. No. 33,464.
U.S. Pat. Nos. 4,654,077 and 4,732,368 describe a method and apparatus, respectively, for the pyrometallurgical treatment of finely divided materials and are incorporated herein by reference. In particular, those patents describe a method and apparatus which uses a combustion chamber having two co-axially extending, vertical chambers to treat materials such as finely divided metal ores to reduce the metal to a pure form. The combustion gases in those patents expand as they enter the first vertical chamber and then expand again as they enter the second vertical chamber creating toroidal recirculation zones at the annular space next to the chamber walls that help to stabilize the combustion flame. Those patents especially disclose combustion methods and apparatus which use coal or similar solid materials as a fuel. (See col. 9, lines 66-68; col. 10, lines 66-68; col. 12, lines 3-5; and col. 13, lines 10-13.) In addition, those patents disclose that a gaseous fuel such as natural gas may also be used. (See col. 4, lines 36-40.)
A need exists, however, for an improved combustor which uses a gaseous fuel such as natural gas to provide a stable flame over a wide range of conditions.